Neural tube defects (NTDs) are common human congenital anomalies whose etiologies remain largely unknown. One of the most promising clues to the causes of NTDs is that women who use vitamins containing folic acid in early pregnancy are at reduced risk for NTD-affected pregnancies. However, the underlying mechanisms by which folic acid reduces risks are unknown. Also unknown is why a substantial proportion of women who take folic acid continue to have NTD-affected pregnancies. This research proposes an extensive NTD gene and risk factor discovery program which focus on etiologies of NTDs by: 1) studying new genetic polymorphisms related to the folate pathway;2) exploring dietary intake of important nutritional factors such as choline and glycemic index, controlling for folate intake;3) measuring specific nutrients and antibodies in midpregnancy sera from women who deliver fetuses/infants with NTDs compared to those who do not;and 4) exploring three unique mouse models pertaining to impaired folate transport to identify new target genes that can be applied to our human studies. This multidisciplinary and integrated 5- year research program will use four large population-based epidemiologic datasets containing data on 1559 infants or fetuses with NTDs and 3353 nonmalformed control infants in combination with state-of-the-art laboratory genotyping methods of human DNA, and will capitalize on unique genetic mouse models to further inform epidemiologic direction. The research program has four collaborating institutions, the California Birth Defects Monitoring Program, the Institute of Biosciences and Technology at Texas A&M University, University of Nijmegen, and Children's Hospital Oakland Research Institute. The research capitalizes on the investigators'collective expertise in molecular and nutritional epidemiology, clinical, molecular, and murine genetics, and teratology. This research program will enhance scientific understanding of the genetic and nutritional causes of NTDs. Because NTDs result in substantial morbidity as well as high emotional and economic costs, further scientific understanding leading to possible prevention would greatly benefit society.